1. Field of the Invention
The present invention relates in general to head gear display systems which provide visual information to the wearer of the head gear display system simultaneously with an external scene in the eye of the wearer's field of view.
2. Description of the Related Art
Head gear display systems, sometimes referred to as "helmet display systems", "head mounted displays", and "head-up display systems", and the like, are those which generally allow for the simultaneous viewing of visual information and/or images generated by a computer or other source, together with, and/or superimposed on, a direct viewing of an external scene are well-known.
Such head gear display systems find utility in many areas, such as training, machine control, or entertainment. Such systems have found particular utility in military applications where information must be supplied to vehicle operators and weapons controllers. Aircraft pilots find such systems useful to furnish information relating to aircraft operation, weather radar presentations, maps, weapons aiming, and other such information as would be useful or desirable in their flight mission.
In some systems, the visual information or visual images are superimposed on an optical combiner mounted on the head gear, sometimes a helmet visor, in view of the eye of the wearer, i.e., the observer's line of sight. These visual images may be derived from a variety of display sources including cathode ray tubes, fiber optic displays, flat screen liquid crystal or electroluminescent devices, some including image enhancers, and even photographic projectors operating with an appropriate optical relay system, all of which may supply the observer with visual information.
Helmet mounted systems for displaying images are well-known in the art. U.S. Pat. No. 3,059,519, issued to Stanton, taught a helmet mounted display in which a CRT display was directed through an optical system that included a plurality of reflecting mirrors which ultimately placed the image in the eyes of the observer slightly above the normal line of sight.
U.S. Pat. No. 3,787,109, issued to Vizenor, disclosed a display where a helmet was provided with a pair of paraboloidal visors, serving as an optical see-through combiner or mirror, with a partially reflective coating on the inner surface as the primary optical element in reflecting the display source image from the visor to the eye of the observer.
U.S. Pat. No. 4,465,347, issued to Task et al., discloses a system in which the image is derived from a telescopic optical system which projects the image on an inner surface of the visor. The visual image is reflected to a planar mirror on the helmet and to the visor again where it is directed into the eye of the viewer and it appears to be part of an external scene.
A substantially more complex helmet display is disclosed in U.S. Pat. No. 4,361,384, issued to Bosserman. Disclosed is a device which combines a thin film flat panel display and a wafer diode image intensifier tube. A plurality of semi-transparent optical systems direct the visual image from the flat panel display into the eye of the observer. The image intensifier, using some of the same optics, also directs a visual image into the eye where it can be super-imposed over the images received from the external scene as observed through the visor. The observer thus views the exterior through both the visor and the flat panel display images. The visor, for reflecting purposes, may be holographic, toric, aspherical, or spherical.
U.S. Pat. No. 4,026,641, issued to Bosserman et al, discloses a head gear display system including a fiber optic bundle having a toric convex object surface which serves as an optical transfer device to transfer visual information from the auxiliary display to the toric convex object surface. In turn the visual image is directed towards a toric optical combiner which serves to direct the visual image toward the eye of the wearer of the head gear display system.
For the most part, prior art head gear display systems employ generally an on-axis optical system (i.e. symmetrically arranged around the central optical axis, sometimes folded), including optical elements internally employed for a projection system for projecting the visual image onto a head gear visor which serves as an optical combiner. However, U.S. Pat. No. 4,968,117 describes employment of an aspheric combiner with a complex projection system, including prisms and a series of optical elements, whose optical axis is off-axis relative to the exit images from a prism face. The optical system disclosed illustrates an optical relay system and following scheme for collimating the visual image toward the eye of the wearer of the head gear display system.
A problem with each of the prior art head gear display systems presently available has been their size and bulk. This is primarily due to the optical systems chosen to achieve the intended function. A second problem with systems of the prior art is their shortfall in providing greater eye relief.